Temperature control mold



May 6, 1947. R. J. MILLER TEMPERATURE CONTROL HOLD Filed Sept. 14,- 1942IN VEN TUR.

. f i 0. i3 v wf/0% 0%.V O 0 u i A Patented May '6, 1947 uNi'rEo STATETEMPERATURE CONTROL MOLD l Raymond J. Miller,

direct and -mesne assignments, to

Detroit, Mich., asslgnor, by

Miller Engl neering Corporation, Detroit, Mich., a corpo.V

ration of Michigan Application September 14, 1942, Serial No. 458,265 i20 Claims.. (Cl. 22-113) This invention relates to the art of castingand more particularly to a simple and economical mold to control thetransfer of heat from molten alloy or metal to delay solidication oflighter molten sections, land to accelerate the solidiiication ofheavier molten sections to reduce undesirable effects of shrinkagestrains caused by the heavier sections of the casting solidifying andattempting to draw metal from lighter sections of the casting alreadysolidiiled.

Cooling of a casting begins immediately upon the molten alloy or metalbeing poured into a mold, and when the temperature drops to apredetermined degree the molten alloy or metal solidies to form thecasting. Solidication of molten alloy or metal is accompanied byshrinkage or a reduction inlvolume due to contraction of the spacebetween molecules of the alloy or 4 metal upon passing iromva liquid tothe solid state.

The period of time required for molten alloy or metal to solidifydepends upon the rate of heat transfer therefrom. Where the casting hassections of varying volume, the period of time required forsolidiiication depends upon 'the ratio of the area of the coolingsurface of the mold to the volume of the casting, and is influenced bythe rate of heat transfer over various sections of the mold.

In the formation of castingshaving sections of varying contour, thelighter moltensections have a greater ratio of surface area to volume incontact with the mold cavity than do the heavier sections. The thinnersectionstherefore cool more rapidly and will solidify while the heaviersections o f the casting are still molten.

In castings having light or thin sections between heavy sections and thefeeder, the thin sections tend to solidify while the heavy sectionsremain molten. As the thin sections jell or solidify they form a pointofanchorage for the molten alloy or metal and also cut oi the heavysections from the shrinkage compensating supply of molten alloy or metalfrom the feeder.

The supply of molten metal or alloy in the pensating for shrinkage.Whensolidication oi the heavierr sections of the casting occur shrinkagestrains of considerable magnitude are set up in the casting because ofthe isolation of the heavier sections from the supply of molten alloy ormetal to maintain the mold completely lled.

In order to prevent shrinkage strains in castings it is desirable thatthe feeder be accessible v to and remain in communication with theventire casting tosupply molten alloy or metal to maintain the moldcompletely filled with alloy or metal until the entire casting hascompletely solidified. This may be most easily effected by controllingthe cooling of the casting lto cause 'all sections of the casting tocool progressivelyv remote from the shrinkage com-v` from pointspensating supply of metal in the feeder chamber towards said chamber. Acontinuoussupply. of molten alloy or metal'will therefore be availableat all times to maintain the mold. completely iilled and prevent theintroduction ofshrinkage strains caused by one portion ofthecastingattempting to draw metalv from surrounding solidied portions.

To obtain this desirable progressive cooling in castings having variedcontours and eliminate the undesirable eiects of shrinkage strains it isAnecessary `to dissipateheat more rapidly from the larger or thickersections and to retard the. transfer of heat from the thin or lightersec y tions.

When molten alloy or metal is poured into a mold to form a casting, anenvelope or skin is formed on the outer surface of themolten substanceby contact with the air or gases within the mold. If themolten alloy ormetal is poured f into the mold slowly and ata substantially con.

feeder chamber to compensatefor reduction in stant rate theenvelope 'orskin can be progressively expanded to surround the entire casting andmaintained throughout the ,entire .castinguntil the solidificationoccurs substantially pro.. gressively or uniformly over the entirecasting.

This envelope ori skin formed on the outside of the molten'alloyjA orVvmetal contacts the surface of the mold cavity and is maintained v duringcooling of the molten alloy or metal. The resulting casting face freefrom roughness due to a breaking-of the surface skin or. envelope. Byyeffectively maintaining the feederopen until the entire has a netextured smooth: surf 3 casting solidiiles, a more solid casting havinghigher physical properties 4less susceptible lto warpage results. y I

In the so-called Capaco process of casting as disclosed in Patent No.2,201,037, issued May 14, 1940, plaster is used as the mold body. Duringthe formation of the plaster mold an excess of moisture is present andthe plaster mold is there- 'after subjected toa drying process wherebyvirformed of low heat conducting material particularly of the so-calledplaster type. -Varies almost in direct proportion to the externalsurface area of the mold to the unit volume of the casting to be formed.By .increasing the ratio of external surface area to the volume of themold cavity over the. thicker or heavier sections of the casting therate of heat dissipation may be accelerated. Likewise by reducing theratio of the external surface area to fthe volume of `the mold cavitythe rate of heat dissipation from the thinner portions of the castingmay be retarded.

No means has heretofore been available to vary e l 35 bers in a desiredspaced relation to form a mold the rate of heat transfer from castingsformed in. low heat conducting materials suchas plaster molds. The useof the so-called plaster molding process has therefore been limited toobjects having substantially uniform cross section or objects whereinshrinkage strains caused by uneven cooling of various sections of thecastings would not be unduly objectionable. In order that this processmay be used in the casting of articles having varied cross sections itis necessary that some means be available to' compensate for variationin thickness of the sections of a casting to permit progressive coolingof all sections of the castirisr towards the point of feed.

My copending application, Serial No. 455,862, led August` 24, 1942,discloses a plaster mold wherein the ratio of the external surface areaof the mold is substantially proportionate to the volume of the moldcavity throughout. These temperature control molds may be formed betweena pattern of the article to be cast and a contour forming member for theexternal surface of the mold. An external mold contour'forming membermust of necessity be made for each article to be cast. .While excellentresults can beaccomplished by the use of that method, the expenseinvolved in making the mold former is disproportionately high where onlya few castings of an article are desired. j

An object of this invention resides in the provision of a simplifiedplaster mold forming member to facilitate the formation of plaster moldshaving external surface area substantially proportionate to the volume'of the mold cavity throughout.

Another object of the invention is to provide a plaster mold formingmember having movable pegs adapted to be positioned in varied spaced lrelation to a pattern to form a plaster mold having a substantiallylproportionate ratio of external surface area to the volume of moldcavity. Y:

may be controlled to provide substantially pro- 6 gressive coolingtowards the 'feeder over' the entire area of the casting.

Another object of the invention resides in the provision of a simplifiedmethod for controlling the rate of heat transfer from a casting byaccel- 10 erating the rate of heat transfer from thicker or heaviersections and delaying the rate of heat transfer from thinner or lightersections of the casting.

A further obj ect is to provide a relatively porous mold having aprogressively decreasing ratio towards the feeder, of external surfacearea to the volume of sections of varying contour of the casting to beformed to control the rate of heat transfer from molten alloy or metalto give progressive cooling towards the feeder.

Yet a still further object ofthe invention 'residesin the provisipn of alow heat conducting mold having' an apertured surface toincrease theexternal surface area and hence therate of heat g5 transfer of portionsof the mold surrounding thicker or heavier sections of the casting.

Yet another object resides in the provision of an economical method offorming temperature control mold sections having cooling surface areaproportionate to the cross section of castings throughout to controlthe'rate of heat transfer from sections of varied contour. A furtherobject is to provide a simple and emcient method of lholding apertureforming memhaving varied surface area.

Another object is to provide av plaster temperature control mold formedof low heat conducting material having a substantially constant 40volume of mold forming substance throughout to permit moisture 'toescape uniformly over the mold surface to insure substantially uniformdrying of the mold.

' Other objects and advantages of this invention will be apparent fromthe following detailed descripticn consideredin connection with theaccompanying drawings, submitted for purposes of illustration only, andnot intended to define the scope of the invention, reference being hadfor 5o that purpose to the subjoined claims.

In the drawings wherein similar reference characters refer to similarparts throughout the several views:

Fig. l is a sectional view of a typical article to be formed.

Fig. 2 is a sectional View of a pattern for forming the article of Fig.1 having a temperature con..

trol mold former superimposed thereon.

Fig. 3 is a sectional view of the temperature control forming mold formaking a plaster mold having variable external surface area to providedifferent rates of heat transfer' over various portions thereof.

Fig. 4 is a plan view of the former illustrated in Fig. 3. n Fig. 5 is asectional view of a temperature control plaster mold having a castingtherein.

Fig. 6 is a sectional view illustrating a modified form of holdingmechanism for the recess forming members.

l Fig. 7 is a fragmentary plan view of a mold embodying recesses of adifferent shape.

Fig. 8 is an elevational view showing a tapered recess forming member.

Il Referring now to the drawings. Fig. 1 is illusaxially extending anges24 on a hub member 28..

The hub and rim are interconnected by a plu.. rality of radiallyextending spokes 28 of relatively small cross sectional area inproportion to the cross sectional area of the rim 22. The ratio of thevolume to the externalsurface area of the rim 22 and anges 24 of thearticle 28 is much greater than the ratio of the volume .to the ex'ternal surface area of the spokes 28. The ratio' of the B. t. u. or heatcontent of large molten sec-y tions in proportion to the area of themold cavity is therefore higher than the B. t. u. or heat content of thesmaller molten sections in proportion to their area in contact with themold cavity.

In the casting of the article 28, such' as the flywheel, a feeder wouldpreferably be positioned at one side of the rim 22 to supplymolten alloyor" metal through'the rim 22 and spokesl 28 to the hub 26.

If no means are provided for controlling the rate of heat transfer fromthemolten alloyv or metal of which the casting is formed, the. spokes28, having greater external surface area in proportion to the B. t..u.or heat content of their molten metal will be subjected to more rapidcooling and will reach the solidification point before the rim 22 andhub member 28 wherein the ratio of the B. t. u. or heat content to themold cavity is considerably higher.

After the alloy or metal forming-the spokes 28 cools to a substantiallypredetermined point it will jell and solidify and the flow of moltenalloy or metal to the hub 28 will/be cut off. As the mass of alloy ormetal forming the hub 26 solidifies it shrinks or contracts and attemptsto draw metal from the spoke ,forming sectionsV 28.

Since the supply of molten metal to the hub y 28 is effectivelyinterrupted by solidiflcation of the alloy or metal forming the spokes,shrinkage of the hub 28 upon solidication results in a force beingexerted to draw metal through the spoke forming segments and shrinkagestrains of con siderable magnitude result. The resulting casting is nothomogeneous or solid' and does not possess the desired degree ofstrength. The casting is pre-stressed and is susceptible of warping, andin any ensuing machining operations or use whereby strains would berelieved, further warping results.

Flg. 5 illustrate a temperature control mold 38 having upper and lowersections 32 and 34. The mold 38 is Vpreferably formed of a low heatconducting porous moldable substance, or a substance such as plastersusceptible of being rendered porous after being formed.

The rate of heat dissipation of such material by radiation is almostdirectly proportional to the ratio of the external surface area of themold to the volume of the mold cavity.

The cooling effect of the mass of the body portion of a low heatconducting material such as aA the casting at any point.

In order t'o effect uniform cooling of sections of varied volume of thearticle to be cast in the mold 88, the ratio of the heat radiatingsurface of the mold should substantially be in direct propor-l v tiontothe volume of the articie' to be cast. By

progressively decreasing the ratio of the external mold surface to thevolume of the moldjcavity heavier portions towards th'e feederprogressive cooling towards the point offeed may beI accomplished. j

Controlled cooling may thus be effected whereby all parts of the castingcool progressively towards the feeder, and the feeder and the lightersections of the casting are maintained open until l the heavier orthicker sections of the casting solidify. Since a constant supply ofmolten metal is' available from the feeder, shrinkage of the metal willmerely draw more molten alloy or metalfrom the shrinkage compensatingfeeder ch'amber and shrinkage strains will be eectively avoided.V

y Whne the meid a0 may be formed of upper and f trol mold 38 may, forexample, be formed with a-plurality of relativelyciosely spaced recessesor apertures 88 terminating close to the sections of largervolume of thearticle28, such as around the rim 22- and flanges 241mg over the hub 28respectively, to increase the ratio of the external surface area of themold Ato the volume of the mold cavity to permit rapid transfer of heatfrom these portions of the heavier sections of the casting. The recesses36 should terminate a sufficient distance from the article to be castvto provide the moldV with sufficient strength to adequately support thealloy or metal 48 poured into the mold 38 to form the article 28.

The mold 38 over the spokes 28 may be relatively thick and provided withfewer recesses lor area to the volume of the mold cavity to producesubstantially uniform or progressive cooling of the casting.

The size of the mold 38 is dependent on the size and contour ofthearticle 28 to be cast, the amount of heat to be dissipated from thealloy. or metal of which the article 28 is formed 'Il'he rate of heatconductivity of thesubstance of which the temperature control mold 38 isformed, the rate` of heat transfer from the surface of the mold 38 tothe atmosphere and other factors.

The lower section 34 of the temperature control 4mold 38 may besupported during the casting operation at its edges to permit air tocirculate freely into the apertures 38. If the article being formed isso large that the mold could not be supported at its edges it may besupported on a suitable framework or' on downwardly extending feet orflanges positioned to underlie the of thearticle to be cast.

' The upper section 32 of the mold 38 may be formed with a riser andfeeder member 42, The feeder'and riser forming member 42 is formed witha feeder'chamber `44 to supply molten alloy or metal through apassageway 46 to compensatefor shrinkage of the casting. The feeder 44 7is surrounded by a suitable mass 46 of the substance from which the mold30 is formed to decrease the-ratio of external surface area to volume ofthe mold cavity at this portion to prevent solidication of alloy ormetal in'the feeder The sections 32 and 34 of the temperature con..`

trol mold 30 may be formed between male production patterns of thearticle. to be cast .and suitable contour forming members superimposedon the pattern. J v

As illustrated in Flg. v2, a male production pat#- tern 50 is suitablyattached to a flask 52 having side wall members 54. The flask may be ofany desired contour such as round, rectangular, etc., to accommodate thepattern 50, A cover plate 56 having a plurality of spaced apertures 66therethrough may be superimposed on the side walls 54 of the flask 52,and may be located in` a predetermined angular relation thereto abledowelpins 60.

The apertures 58 may be of uniform size and may Vbe closely spaced asillustrated in Fig. 4, and are adapted to receive vertically movablemembers or pins 62 adjustably mounted therein to vary the distance fromthe bottom ends. 64 of by suitthe members or pins relative to the coverplate Any suitable means may be provided to maintain the members 62 inany vertically adjusted position relative to tl'e plate 56. An aperturedI `a l i ing ofthe casting may belcontroiled by varying the height'l ofthe lower 'ends 64 of the plnl l2 above the pattern I.4 For example, themold Il over the heavier sections 22. -24 and 24 ofthe article 2l to becast, mayhave many closely spaced apertures 66 terminating close to themold cavity. The mold Il` over the lighter or' thinner sectims 26 of thearticle to be cast may have relatively few apertures 36 terminating agreater distance from thevmold cavity toreduce the ratio of the surfacearea to the volume of the mold substance and delay the transfer of heatfrom the lighter porl tions of the mold.

' After the recess forming members 62 have been adjusted vertically tovary the external mold surface to accelerate the transfer of heat fromheavy sectionsof the casting and to retard the transfer of heat from thelight sections of the casting, the

v mold forming substance may be introduced inw resilient sheet 66, suchas a sheet of rubber, may

be attached to the cover plate 56 to engage the pins 62 and hold them inany vertically adjusted Position to which they are moved.

Ring springs 61 positioned in slots 69 in the plate 56 may also be'employed to engage the recess forming members 62 to hold them in anyvvertically adjusted pOsition to which they are moved as illustrated inFig. 6. y

The recess forming members62 may be of any desired contour in crosssection to provide recesses of varied configuration such for examplesasthe' hexagonal recesses 1| illustrated in Fig. 7.' As illustrated inFig. 8 the recess forming members 13 may be tapered to provide the moldsurface with varied external surface area. and to facilitate thedissipation of moisture and heat from the mold during the drying of themold vand the cooling of the casting.

In the formation of the sections of the mold 3U. any suitable moldforming substance such as low heat conducting plaster may be introducedinto the space Within the flask 54 to cover the pattern 50 to a desiredheight on the pins 62. The cover plate 56 may be assembled on. the iask52 having the pattern 50 therein. lThe pins 62 may then be pusheddownwardly into contact .with the surface of the pattern 50. The coverplate -56 maythen be elevated and a spacer 68 interposed betweenl theside walls 54 of the ilask andthe cover plate 56 to elevate the lowerends 64 of the pins 62 a predetermined distance above the surfaceof thepattern 50. Spacers 68 of different thickness may be provided for use informing temperature control molds for various articles.

'Ihe ratio of the external surface area to the volume of the mold cavityand hence the rate of coolthe flask through an opening 1l, airbeingpermitted to escape through another of these openings. The quantity ofplaster or other mold forming substance employed is dependent on thenature and size of the casting to be formed, the rate of'heat transfer,etc..

The portions pr the pins or pegs 62 projecting into the mold formingsubstance may be coated with any suitable parting material 12 tofacilitate.

separation of the pe'gsfrom the mold forming substance.

If desired the lcover piste n and the resilient sheet 64 may betransparent to such an extent as to enable the molder to observe theposition of the lower ends 64 of the pins 42 relative to the pattern'54. Where the pins 42 are of uniform length the outline of the pattern'6l will be reproduced at the upper ends of the pins 42 projecting abovethe cover plate 56 to aid .the molder in making the necessaryadjustments. The diameters of the pins may be varied if desired to givemore definite control of the external surface area of the mold.

The composition of the plaster or other moldA forming substance ispreferably such as to fornia relatively porous mold structure wherebygases formed during the casting operation and entrained air may readilyescape through the body of the mold. `This relatively porous plastermold structure may be achieved by initially mixing the plaster formingingredients with somewhat of an excess of moisture and .thereafterdrying the mold to drive of! virtually all of the moisture.

The mold 30 is preferably such as to adequately supPOrt the casting whenpoured but does not possess suilicient strength to resist the forces towhich -it is subjected when the casting shrinks upon solidication.shrinkage of the casting may, therefore, crack or break` up the mold andthus avoid the introduction of shrinkage strains within the casting. Y

'I'he upper section 32 of the mold 3l may be interlocked with the lowermold section 34 by means of circumferentially extending interlocking Yiianges 14, and the sections 32 and 34 may be held together by means ofsuitable clamps 14.

In the casting of an article 2li in the temperature control mold 3l,molten alloy or metal 4l is introduced through the opening in the feederpositioned at any convenient place as at one side or in the middle ofthe mold. The molten alloy or metal 46 hows through the controlled gate46 into the space within themold Il and completely mls the space withinthe mold 3l. Y

Gases formed upon contact of the molten alloy or metal 4l with theinternal surface of the mold The upper and lower sections 32 and 34 ofthe mold 30 dissipate heat from the molten metal 40 v substantiallyuniformly over the entire area of the casting. The increased externalsurface area of the mold due to the presence of the recesses or holes 36coupled 'with the sections of relatively thin mold section over heavyportions of the casting permit rapid dissipation of heatffrom theheavier sections of the casting, and the walls of the mold having lessapertures tend to retain the heat in the thinner sections of thecasting, such, for example,as the spokes 28.

Virtually the entire casting cools progressively or simultaneously. Thecontrolled supply gate 48 and the feeder chamber 44 provide an amplesupply of molten metal to compensate for contraction of metal uponsolidiiication. Thethinner spoke forming sections remain molten duringcooling of the heavier sections andv all parts of the casting solidiiiesprogressively towards the feeder or simultaneously.l

' If desired, air may be circulated over the mold f .sections to assistin the dissipation'of heat from the mold. The cooling air may becontrolled as to direction to subject only a portion of the mold 30 tothe cooling action, to give more accurate and positive control over thecooling of the casting. The temperature of the air directed overthevmold 30 may'also be controlled-to producel the desired cooling ofvarious portions of the casting f to insure uniformcor progressivesolidiflcation of the casting.

When a plaster mold is subjected to a drying l action the entrainedmoisture in the mold is transferred to the surface ofthe mold bycapillary attraction, and it is transferred to the atmosphere from theVexterna1 surface of the mold. Largemasses of solid plaster delay thetransfer of moisture to the surface, whereas small sections or sectionshaving a larger ratio of surface Aarea to volume readily transfermoisture to the surface for dissipation tothe atmosphere. In moldshaving wide variation in sections, unequal drying action results andthelighter or thinner sections are'likely-to become burned and crack beforethe heavier-,orthicker sections have had an oppor-A mberor the-depth o fthe tions .v of theqarticle t0 be seglofjfa -suilcientL number ofiermold sections, positioned to during they drying v operation'.`Uniform drying of the mold may thus beeffected-and since these recessesv'are formed in' the mold forming vsubstancetheyihave a` desirableeffect on dissipation of heatfromfthefcasting. g Accurate control of thedissipation Vof-.heat'from thecasting may thus Ifclaimry v l. AtemVrature control'mold forming member comprisinga .ask having a,patternthereim f a plate superimposedforithewfiask'and having aplurality of closely spacedapertures therein,

`a. plurality of recess forming members movably mounted in saidapertures, andresilient means to maintain the recess forming members inany ad.- 5 justed position.

2. A temperature control mold forming member comprising a plate havingclosely spaced apere' tures therein, members extending through andmovable in the apertures, and resilient means to l0 hold the members inany position to which they may be moved.

3. A temperature control mold forming member comprising a ask having a.pattern therein, a plate superimposed on the flask andv having a,

plurality of closelyspaced, apertures therein, a

plurality of pegs extending through said apertures and movable relativeto the plate, and resilient means associated with the plate to hold thepegs in any adjusted position to which they may be moved. .Y

4. A temperature control mold forming member v comprising a plate havingclosely.Y spaced apertures therein, pins extending through andl movablein the apertures, and resilient means carried 5 by the plate to hold thepins in any vertical position to which they may be moved.

5. A mold formingl member comprising a flask having side Walls, apattern detachably connected to the flask, a, recess forming member`supporting plate carried bythe side walls of the ask, locating meansbetween the plate and ask, a plurality of spaced vertically movablerecess forming members carried by the plate, resilient means to hold--the recess vforming members in any adjusted position, a spacer adaptedto be interposed between the flask and the plate', and locating meansassociatedI with the spacer to maintain alignment between the flask andplate.

6. The method of making a temperaturey con- 40 trol mold comprisingsuperimposing on a pattern of an article to be cast a member havingclosely spaced movable recess forming members,l adjusting vthe recessforming'members to contact the surface of the pattern, separating therecess forming members from Ythe pattern by introducing a spacer beneaththe member, withdrawing recess forming members over light sections ofthe .casting, and applying to the exposed surface of the pattern andpins a substance capable of being rendered substantially porous toprovide a mold having a substantially constant ratio of external surfacearea to the volume of the article to-be cast.

7. The method of forminga temperature -control mold for castings havingvarying contours comprising superimposing on a pattern of the article tobe cast a plate having closely spaced vertically movable pegs, adjustingthe pegs vertically relative to the pattern in proportion to `variationsof volume of the casting, and introducing plaster, around the'patternanddownwardly projecting ends of the pegs to form a temperature controlmold having large external surface area surrounding heavy sections ofthe article to be cast and relatively less externalsur..

' face area over lighter sections of the article to be cast.

8. The method of making a plaster temperature'controlmold comprisingsuperimposing on a pattern of an article to becast a plate havingclosely spaced adjustable recess forming members, adjusting the recesslforming members t0 contact the surface of the pattern, separating therecess forming members from the pattern by introducing a spacer beneaththe plate, withdrawing recess' forming kmembers over light sections ofthe casting,. applying plaster to the exposed surface of the pattern andrecess forming members to form a temperature control mold having a ratioof surface area to volume substantially prosuperimposed on the frame toform spaced re cesses in the external surface of the mold, manuallyoperable means to selectively vary. the spacing of the recess formingmembers'from the pattern, and means to hold the recess forming membersin'any adjusted position.

10. A mold former comprising a flask having a pattern therein, anapertured plate having mold recess forming members superimposed on thepattern to form spaced recesses in the external surface of the mold toreduce the ratio of the mass of the mold forming substance to itsexternal surface `area throughout to facilitate the transfer of moistureto the surface of the mold and accelerate drying of the mold, means toselectively vary the spacing of the recess forming members from thepattern, and means to hold the recess forming members in any adjustedposition.

11. The method of forminga non-permanent mold formed of low heatconducting material comfprising superimposing on a' pattern amoldcontour former having closely spaced parallel `mold recess formingmembers of generally circular cross-section for shaping the externalsurface of the mold to provide a mold forming space sub- `stantially ininverse proportion to the volume of sections of varying contour of thecasting to be formed, lling said space with a low heat conducting moldforming substance, separating the mold from the pattern and contourformer, and

thereafter drying the mold.

12. A non-permanent temperature control mold formed of low heatconducting material to prevent the formation of shrinkage strains in acasting having a feeder and sections of varying cross-sectional area,the external surface area of the mold being contoured with closelyspaced generally circular recesses extending substantiallyperpendicularly to the external surface of the mold so arranged as todispose the mass ofI the mold material substantially in inverseproportion 'to the cross-sectional area of the casting throughout tovary the rate of the dissipation of heat by conduction from sections lof varying cross-sectional area of the casting to prevent the formationof solidified sections betweenthe feeder and a portion of the casting.

y 13. A non-permanent mold formed of low heat conducting material forforming a casting having sections of varying cross-sectional areacomprising'a body portion havingran external surface provided withsubstantially perpendicularly extending generally circular recesses to.increase the ratio of the surface area of the mold to the mass of themold forming substance to reduce the distance moisture must travel toreach the external surface of the mold to accelerate drying of the moldwithout introducing mold shrinkage strains.

14. A non-permanent temperature control mold formed of low heatconducting material comprising a. body portion having va casting cavityand including a substantially at external surface having a plurality ofrecesses of generally circular cross section extendinginwardly towardthe casting cavity substantially pl'pendicularly to the ilat externalsurface ofthe mold so arranged as to` vary the mass of the mold formingmaterial substantially in inverse proportion to the volume of sectionsof varying cross-sectional area of the casting to be formed.

15. A temperature control mold havinga casting cavity for the receptionof molten alloy or metal to form a casting having sections of varyingcross-sectional area comprising a dried mold formed of low heatconducting material having closely spaced recesses of generally circularcross section extending substantially perpendicularly from the externalsurface of the mold to points adjacent the castingcavity over sectionsof thel casting of large cross sectional area to increase the ratio ofthe external surface area of the mold -to the cross sectional area ofthe casting and permit the rapid transferv of heat from heavy portionsof the casting, and spaced recesses extending substantiallyperpendicularly from the external surface of the mold to pointsprogressively more remote from the casting cavity over sections of lthecasting of progressively smaller cross sectional area to progressivelyincrease the ratio of the external surface of the mold t0 the crosssectional area of the casting but to a lesser degree than the recessesin the mold over the sections of the casting of greater cross section toretard the transfer of heat from light portions of the casting.

16. A temperature control mold having a casting cavity for forming acasting having sections of varying cross-sectional area comprising abody portion formed of low heat conducting material having closelyspaced generally circular recesses extending substantiallyperpendicularly from the external surface of the mold toward the castingcavity to points adjacent the casting cavity where the cross-sectionalarea of the casting is large and to points more remotely spaced'from thecasting cavity where the cross sectional area of the casting is small.

17. A non-permanent mold formed of low heat conducting materialcomprising a body portion having a casting cavity and a plurality ofclosely spaced parallel recesses of generally circular cross-sectionextending inwardly from the external surface of the mold toward thecasting cavity to provide a honeycomb-like structure to reduce the moldforming material required and to facilitate the drying of the mold byreducing the distance moisture must travel to reach the surface of themold to be expelled.

18. A mold former comprising a pattern, a housing surrounding thepattern. and a plurality of mold recess forming members carried by thesaid housing, said members being shiftable to Y selectively vary theheat dissipating qualities of the mold material.

19. 'Ihe method of making a non-permanen mold formed of moisturecontaining material, which comprises forming in said material, whileitis still wet, a plurality of recesses to'control the heat dissipatingproperties of the material, remov- 13 bers in said material to differentdepths to form closely spaced heat flow paths therein overlying andextending along the casting cavity to regulate the lengths ofthe heatflow paths through said mold material and to vary the heat dissipatngproperties of the mold in accordance with the spacing of the heat flowpaths, and thereafter removing said members.

RAYMOND J. MILLER.

REFERENCES CITED The following references are of record in the ille ofthis patent:

Number Number UNITED STATES PATENTS Name Date Lee Sept. 25, 1928 PackApr. 29, 1919 Lee 'Sept. 25, 1928 Candler Nov. 22, 1927 Sipp July 31,1928 Sweetnam Oct. 23, 1917 FOREIGN PATENTS Country Date British 1912

